The American Cancer Society estimates that more than 5,000 people will be diagnosed with anal cancer this year, and there is little doubt that many will be HIV-positive. Studies suggest that HIVers-in particular gay and bisexual men-are up to 80 times more likely to develop anal cancer than the general population.

Anal cancer has been linked to the human papillomavirus, which is the cause of genital warts. Virtually anyone who has had sex has been exposed to HPV. Typically, it's fairly easy for the immune system to knock out any infection the virus may cause. But for HIVers, HPV is harder to eradicate, making it more likely to progress to cancer.

Like many other physicians, Jeffrey Ellis, a dermatologist in New York, has seen an increase in the number of HIV-positive men requiring treatment for HPV-related anal and genital warts. Well aware that these men are also at higher risk for anal cancer, Ellis refers these patients to colleagues who can provide anal Pap smears, which can detect this type of cancer.

Currently, no national recommendations on routine anal Pap screening exist. A number of HIV specialists, though, now offer their patients annual anal Paps. Those who test positive and need follow-up care are referred to specialists who perform high-resolution anoscopy, which can identify precancerous or cancerous growths in the anal tissue.

Some health advocates have begun promoting annual anal Pap screenings for all HIVers. But as Joel Palefsky, MD, an HIV specialist at the University of California, San Francisco, who founded the first anal neoplasia clinic, notes, it makes little sense to offer anal Pap tests to HIVers who do not have access to a doctor who provides anoscopy screenings as well. Instead, he says, these HIVers "should have an annual digital rectal exam," which is something "that all primary care providers know how to do."

Paul, a 59-year-old HIVer who was diagnosed with anal cancer in 2002, says he hopes the stigma attached to anal cancer will dissipate as more people learn about the disease. In many ways, he says, being diagnosed with anal cancer "felt like going back to having HIV. Here I was again with another unpopular disease that no one is willing to talk about."